This proposal tests the hypothesis that Behavioral Inhibition is an expression of a constitutional predisposition to anxiety disorders in children at-risk for anxiety disorders and is predictive of subsequent anxiety disorders in children. The study includes initial assessments of "behavioral inhibition to the unfamiliar" (Behavioral Inhibition) in 225 children ages 4.0 to 5.9 years, and a follow-up assessment of Behavioral Inhibition and emergent psychopathology two years later. We will sample young offspring of parents with panic disorder and agoraphobia (N=150) and parents having no psychiatric illness (normal comparison children) (N=75). The current proposal would be the beginning of a long term project aimed at assessing the ability of Behavioral Inhibition, assessed at an early age, to serve as a predictor of anxiety disorders in childhood, adolescence and adulthood. Behavioral Inhibition, as described by Kagan and colleagues, is the consistent tendency to display fear and withdrawal in situations that are novel or unfamiliar. Since these responses, which are measured in a laboratory setting, are assumed to reflect low thresholds of limbic arousal to challenge, they may underlie a risk for the development of anxiety disorder. This project is a proposed investigation of Behavioral Inhibition, and in particular, Behavioral Inhibition persisting at follow-up assessment (Stable Behavioral Inhibition), as a potential early predictor for the later development of anxiety disorders. The rationale and main impetus for this study stem directly from our group's prior work with children of parents with panic disorder and agoraphobia and children originally identified in infancy as exhibiting Behavioral Inhibition. The pilot work supports the hypotheses to be tested, the estimation of sample size, and the overall feasibility of this project. Since pilot work suggests that Behavioral Inhibition is a manifestation of the constitutional vulnerability to anxiety disorders, we hypothesize that high Ask children (of parents having panic disorder with agoraphobia) will have higher rates of Behavioral Inhibition and Stable Behavioral Inhibition than children of never ill comparison parents. At a two-year follow-up, more anxiety disorders are expected among children who had Behavioral Inhibition at the initial assessment compared with other children, In addition, the project includes exploratory assessments of the role of environmental factors as additional predictors for Behavioral Inhibition or psychopathology. Studies of children at-risk and the identification of factors responsible for childhood psychopathology are considered to be of highest research priority in the Institute of Medicine's Special Committee Report on "Research on Children and Adolescents with Mental, Behavioral, and Developmental Disorders" and in the National Institute of Mental Health National Plan that followed. The proposed work represents the most comprehensive assessment of children at-risk for anxiety disorders yet undertaken. The products of this research, in addition to early identification of children at highest risk for later development of anxiety disorders, could lead to the design of protocols for primary preventive or early intervention programs.